PROJECT SUMMARY Daily oral pre-exposure prophylaxis (PrEP) is effective in preventing HIV infection. However, PrEP uptake across at-risk populations including men who have sex with men (MSM) may be limited by out-of- pocket costs. Out-of-pocket costs include copays, coinsurance, and deductibles and may be a significant barrier to PrEP initiation and retention even among insured individuals. Despite being a commonly reported barrier to care, little is known about the impact of out-of-pocket costs on PrEP uptake. We propose a mixed methods and modeling study to determine the maximum out-of-pocket costs for optimal PrEP uptake in different populations including Black/African American and Hispanic/Latino MSM. The specific aims of the proposed study are to: 1) conduct 45 semi-structured interviews with MSM to explore how out-of-pocket costs may impact PrEP uptake; and 2) model the impact of co-pays, coinsurance, and deductibles on PrEP uptake. Findings from this pilot study will inform future development of interventions that address cost as a barrier to PrEP uptake, and ultimately improve outcomes in populations at highest risk for HIV acquisition. This study aligns with the high priority topic of identifying gaps in the PrEP care continuum and associated determinants of health, and reducing racial/ethnic disparities in PrEP uptake and use as defined by the NIH and Office of AIDS Research.